Water makes it cheaper and means devices can be made with an inkjet printer.

Supercapacitors complement batteries in energy storage and delivery schemes both large and small, as they can provide quick bursts of power. They already help Honda’s fuel cell vehicle FCX accelerate. But supercapacitors hold less energy per volume than a typical battery, so they have limited storage capacity.

Changing the electrode material can boost the capacitance, thus improving the energy density. Yi Cui and Zhenan Bao of Stanford University have made a hydrogel (water-based gel) using a conducting polymer. When used as electrodes in a supercapacitor, the new material has a capacitance about three times greater than a typical carbon supercapacitor. It’s also cheap to build and operate.

Typical supercapacitors are made from two closely spaced, porous carbon electrodes that charge and discharge quickly. Negative ions from the electrolyte collect inside the pores in the positive electrode, while positive ions gather in the negative electrode. That ion separation stores energy as a potential difference between the two electrodes.

Besides storing ions, supercapacitors made from conducting polymers have an additional form of capacitance called pseudocapacitance. Electrons transferred to and from the polymer strands build extra charge along the chains.

One common conducting polymer is a string of many molecules of aniline, a ringed structure with a nitrogen hanging off. The researchers connected strands of this polymer with a phosphate-covered sugar derived from plants to form the new hydrogel material. The hydrogel looks like foam under a scanning electron microscope. Its 3D branches create a porous structure that provides the material with more surface area to hold ions and charges.

To make the hydrogel supercapacitor, the researchers coated two carbon sheets with the new polymer gel and soaked the electrodes in a dilute solution of sulfuric acid. Then they connected each electrode in a circuit and measured how much charge the supercapacitor could hold.

Aniline worked very well in hydrogel form. The device retained 93 percent of its capacitance when charged quickly with ten times the standard current density. Typical electrodes made from polymerized aniline lose 25-40 percent of their capacitance when charged at higher power. The new material also retained 83 percent of its capacitance when charged at high power for 10,000 cycles—ten times more charging cycles than other polyaniline electrodes.

The researchers say this new material is easier to synthesize than other polyaniline-based hydrogels. Previous conducting polymer hydrogels were limited because they started with a block of non-conducting polystyrene soaked in aniline. A special molecule triggers the chain-forming reaction, or polymerization, of aniline. That creates threads of conducting polyaniline winding through the non-conducting hydrogel.

Because this new material is made mostly from polyaniline, the entire structure can conduct electricity. And its synthesis only requires mixing two solutions: one containing the aniline and the sugar linker, the other containing the triggering molecule. Once mixed, the hydrogel sets within three minutes.

Things are much simpler physically, too. The polymer can be synthesized using inkjet printing or spray coating each solution on a surface. That means it’s easy to make it on a large scale for possible energy storage applications—or even on a tiny scale for microelectronics, the researchers say.

The electrolyte is another factor that makes this conducting polymer supercapacitor attractive for low cost, yet high performance, energy devices. This hydrogel uses a cheaper water-based electrolyte compared to the organic ionic liquids used in carbon supercapacitors.

. But supercapacitors hold less energy per volume than a typical battery, so they have limited storage capacity.... the new material has a capacitance about three times greater than a typical carbon supercapacitor.

So how much less energy does a supercapacitor hold than a battery? Does this three times capacitance move this supercap up to the level where it starts to compete with batteries?

And whatever happened to that EEStor company that was supposed to have breakthrough supercapacitor technology, several years ago?

[moderation="Trolling"]In other news, local man fuels up carbon-monoxide spewing hum-vee using distilled hydrocarbons from fossilized dinosaurs who had an even more primitive outlook on the world than the GOP.[/moderation]

Energy density is a combination of capacitance AND dielectric properties (max voltage, leakage properties). How one can report on a supercapacitor tech and not mention voltage or current figures is astounding! Maybe I'm reading the wrong blog.

Another thing that will be important to commercialization.. stability. I'd imagine a soft jelly energy storage device could possibly release all of its energy faster and more destructively than a li-ion burn, but considering its chemical make up, the smoke may not be as bad to breathe

I'd imagine a soft jelly energy storage device could possibly release all of its energy faster and more destructively than a li-ion burn, but considering its chemical make up, the smoke may not be as bad to breathe

Much as I argue against hybrids and EVs, it's less because I don't like the idea than because I don't like current generation. This seems to address one of the more significant issues.

The problem tho is that arguing against them now may mean that there may never be any money funneled towards future improvements. The first couple of generations will be tired to urban areas, but those are the same areas that has issues with smog and similar. Hell, the gasoline cars was fueled by buying tin cans from drug stores and similar. Hitting the road in one of those was likely seen as a cross between folly and showmanship, much like it is to do so in a EV today.

Wouldn't the gel be used as the dielectric in said capacitors between the conductive electrodes?

Yeah I had to rack my brain on that one. So, I always try to bring it back to basic principles and reason from there. A voltage/electric potential results from a charge separation. Current will always flow in the path of least resistance.

So what happens in a dielectric as you charge it is electrons accumulate on one side of the dielectric, creating the potential. But when you hook it up to a wire, you actually have two paths. The electrons can either migrate back through the dielectric, or through the wire. So the potential through the circuit is the same everywhere, but because the electron mobility in the dialectric is low (i.e. high resistance) and the electron mobility through the wire is high - it will preferentially go through the wire. But, if you disconnected the wire, the charge would gradually migrate back to the other side of the dialectric.

So the thing to keep in mind is that charge can move through any material. The only difference between an insulator and a conductor is the charge mobility - the easy with which the charge carrier can move. So in an insulator you only have negative charge carriers - electrons. The deficit of electrons on one side is what causes the electric potential, because the protons can't move.

In the hydrogel, you have an electrolyte, a salt that separates into positive and negative ions when dissolved in water. This is a much more complex interaction. The electrons are not replacing depleted electrons from the media itself, the hydrogel. They are doing so in one of the mobile charge carriers. The presence of water, which itself ionizes easily, also means there's probably all kinds of weird transient chemical reactions going on, but the principle is the same.

When a current is applied the positive ions will accumulate on the negative electrode and vice versa. So long as the ions cannot migrate through the gel, as quickly as the electrons through the wire there will be a current through the wire.

For those of you that aren’t afraid of units, this paper claims a capacitance of around 480 Farads/gram, while current carbon-based capacitors are at about 120 F/g.

Whoa! Hundreds of Farads per gram? Most of the capacitors I've worked with in my casual studies of electronics are measured in mF, µF or nF.Still - these are CAPACITORS. An old physics teacher told me they are fundamentally limited to no more than 50% energy efficiency, when charged/ discharged once. So while they are VERY useful for applications that require rapid charging/ discharging, and very useful as a component in an energy storage/distribution system; they're never going to constitute more than a small part of the overall system.

For those of you that aren’t afraid of units, this paper claims a capacitance of around 480 Farads/gram, while current carbon-based capacitors are at about 120 F/g.

Whoa! Hundreds of Farads per gram? Most of the capacitors I've worked with in my casual studies of electronics are measured in mF, µF or nF.

Supercaps that use carbon aerogels typically range from .5 to tens or hundreds of Farads, depending on the application (from temporarily powering volatile RAM to soaking up energy for regenerative braking). I guess only a small amount of the actual material is used.

And whatever happened to that EEStor company that was supposed to have breakthrough supercapacitor technology, several years ago?

They still claim to be working on it. They actually issued a [url="http://www.marketwatch.com/story/eestor-provides-a-progress-update-on-the-development-of-its-electrical-energy-storage-units-2012-05-15"]press release[/url] a couple of weeks ago:

Quote:

EEStor has been working on the development of single layer Electrical Energy Storage Units (EESUs) as a step toward full commercial units. The single layers are generally around 20 microns in thickness with an area of 0.25 inches square. EEStor has successfully demonstrated a process that yields layers that can handle an operating voltage in excess of 3500 volts, have a dc resistance of greater than 700 terra ohms, and a dissipation factor of 0.005.

However, the most recently produced versions of the EESU layers have been tested by EEStor and in EEStor's opinion do not yet achieve the level of permittivity necessary for commercial production. EEStor is now working on improvements in the film morphology which it believes will allow it to significantly increase the permittivity and energy storage capabilities of the layers.

But of course, they also state that “The performance of the EESU layers has not been independently tested.”

So, at 480 farads/g, it would take 21 grams of this material to equal a AA battery. That's actually 2 grams less than an alkaline battery, but 6g more than a Lithium battery.

Thanks, I learned something (really)

Despite the 6g more than Lithium, it's still a good development. That's only a small percentage worse than Lithium batteries (and might be compensated by shorter charge times), but magnitudes better than carbon based capacitors.

The "jellies" pictured here look like they'd deform and/or break apart in the presence of any kind of physical stress--are these representative of the actual substance?

Probably representative of the substance itself, but not of actual capacitor devices; I believe this would just be the pure gel pictured for demonstrative purposes (possibly dyed for effect; yummm!). The article text speaks of making the gel with inkjet printers and such, which suggests extremely thin layers of the stuff. So mechanical deformation is probably not much of a concern at that scale - unless you hit the cap with a hammer of course.

...Which, if it really stores 400+ F charge ought to create one hell of a bang, I'd think! I once saw a 1F cap in the power supply of a brushless motor-powered plotter, this was back in '92 or such I think. It was absolutely MASSIVE, way bigger than a 33cl can of soda. To think tech has moved on this much since then is quite astonishing.

Trivia... The moon rocket Tintin & gang travelled in had an auxiliary engine powered by aniline and liquid oxygen as I recall. This capacitance gel might thus be rather explosive... (Reference movie "Demolition Man", again for effect... Heh.)

Can anyone tell me what the time delay on these "breakthrough" storage methods between proof in a lab and commercial application. I know I've read a handful of really interesting articles about this stuff over the last 5 years, but none that I can remember have come to market that I know of. Perhaps it's often too subtle to notice, but damn it I want to see something amazing happen.